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Macropsia
| ICD9 = | ICDO = | OMIM = | MedlinePlus = 003029 | eMedicineSubj = | eMedicineTopic = | MeshID = D014786 |}} Macropsia (also known as megalopia) is a neurological condition affecting human visual perception, in which objects within an affected section of the visual field appear larger than normal, causing the subject to feel smaller than they actually are. Macropsia, along with its opposite condition, micropsia, can be categorized under dysmetropsia. Macropsia is related to other conditions dealing with visual perception, such as aniseikonia and Alice in Wonderland Syndrome (AIWS, also known as Todd’s syndrome). Macropsia has a wide range of causes, from prescription and illicit drugs, to migraines and (rarely) complex partial epilepsy, and to different retinal conditions, such as epiretinal membrane. Physiologically, retinal macropsia results from the compression of cones in the eye. It is the compression of receptor distribution that results in greater stimulation and thus a larger perceived image of an object. Signs and symptoms The most obvious symptom of macropsia is the presence of exceptionally enlarged objects throughout the visual field. For example, a young girl might see her sister’s books as the same size as her sister. Stemming from this symptom, someone with macropsia may feel undersized in relation to his or her surrounding environment. Patients with macropsia have also noted the cessation of auditory function prior to the onset of visual hallucination, indicating possible seizure either before or after the hallucination. A buzzing sound in the ears has also been reported immediately before macropsia development. Some patients claim that symptoms may be eased if an attempt is made to physically touch the object which appears enormous in size.Macropsia. Schneck JM. Am J Psychiatry 121:1123-1124, May 1965 It is important to note, however, that patients typically remain lucid and alert throughout episodes, being able to recount specific details. A person with macropsia may have no psychiatric conditions. Symptoms caused chemically by drugs such as cannabis, magic mushrooms, or cocaine tend to dissipate after the chemical compound has been excreted from the body. Those who acquire macropsia as a symptom of a virus usually experience complete recovery and restoration of normal vision. Dysmetropsia in one eye, a case of aniseikonia, can present with symptoms such as headaches, asthenopia, reading difficulties, depth perception problems, or double vision. The visual distortion can cause uncorrelated images to stimulate corresponding retinal regions simultaneously impairing fusion of the images. Without suppression of one of the images symptoms from mild poor stereopsis, binocular diplopia and intolerable rivalry can occur. Psychological effects There are a broad range of psychological and emotional effects that a person suffering macropsia may experience. One competing theory has radically stated that macropsia may be an entirely psychological pathological phenomenon without any structural defect or definite cause. He or she may be in an irritable or angry state, or in contrast, a euphoric state. There is evidence that those who experience Alice in Wonderland Syndrome and associated macropsia are able to recount their experiences with thorough detail. There may be no evidence of psychiatric disturbance and, as a result, no psychiatric therapy may be required. Psychological conditions often arise from macropsia, but the general consensus is that they do not cause macropsia. Those afflicted may experience extreme anxiety both during and after episodes as a result of the overwhelming nature of his or her distorted visual field. Due to the fear and anxiety associated with the condition, those who have previously suffered an episode hesitate to recount the episode, although retain the ability to do so. Psychologically, a person with macropsia may feel separation and dissociation from the outside world and even from immediate family. This feeling of dissociation has mostly been noted in child or adolescent patients. The patient may feel that he or she must unfairly contend with hostile and aggressive forces due to the gigantic nature of the surrounding environment. The defense against said forces is usually expressed verbally. The patient may falsely present an outgoing or flamboyant persona, while remaining fearful of people internally. He or she, in an attempt to balance the size distortion, may try to make others feel small in size through insult or hostile behavior. The psychological impact of macropsia on long time sufferers who have had the condition since childhood may be greater and lead to severe ego-deficiencies. An alternate interpretation of the condition is that macropsia is a response to biophysiological contraction and has no psychological roots. Thus, when a patient reaches for an enlarged object, he or she is overcoming that physiological contraction .Raphael, C.M. Macropsia. 122 (1): 110 Am J Psychiatry However, this theory has been under much scrutiny. Causes Structural defects In cases where macropsia affects one eye resulting in differences in the way the two eyes perceive the size or shape of images, the condition is known as aniseikonia.de Wit GC, Muraki CS. Field-dependent aniseikonia associated with an epiretinal membrane a case study. Ophthalmolgy 2006; 113:58-62. Aniseikonia is known to be associated with certain retinal conditions. Epiretinal membrane has been found to cause metamorphopsia and aniseikonia.Benegas NM, Egbert J, Engel WK, Kushner BJ. Diplopia secondary to aniseikonia associated with macular disease. Arch Ophthalmol. 1999; 117:896-899.Enoch JM, Schwartz A, Chang D, Hirose H. Aniseikonia, metamorphopsia and perceived entoptic pattern: some effects of a macular epiretinal membrane, and the subsequent spontaneous separation of the membrane. Ophthalmic Physiol Opt. 1995; 15:339-343.Kroyer K, Jensen OM, Larsen M. Objective signs of photoreceptor displacement by binocular correspondence perimetry: a study of epiretinal membranes. Invest Ophthalmol Vis Sci. 2005; 46:1017-1022.Ugarte M, WIlliamson TH. Aniseikonia associated with epiretinal membranes. Br J Opthalmol. 2005; 89:1576-80. Vitreomacular traction caused by the excessive adhesion of vitreous fluid to the retina is related to aniseikonia due to the separation and compression of photoreceptor cells. Macular edemaSjostrand J, Anderson C. Micropsia and metamorphopsia in the re-attached macula following retinal detachment. Acta Ophthalmol (Copenh). 1986: 64:425-32. and surgical re-attachment for macula-of rhegmatogenous retinal detachment can also cause an increased separation of macular photoreceptor cells resulting in dysmetropsia. Retinoschisis is another eye disease that has been shown to cause aniseikonia.de Wit G.C. Retinally-induced aniseikonia. Binocul Vis Strabismus Q. 2007; 22:96-101. There is evidence that a lesion appearing in the posterior area of the ventral occippitotemporal visual pathway can cause macropsia. This lesion can be due to an ischemic cell death after an acute posterior cerebral infarction.Park, M. G. , Joo, H. , Park, K. P., & Kim, D. S. (2005). Macropsia caused by acute posterior cerebral artery infarction. J Korean Neurol Assoc., 23(5), 655-658. Medications The most prevalent research on prescription drugs with side effects of macropsia deals with zolpidem and citalopram. Zolpidem is a drug prescribed for insomnia, and although it has proven beneficial effects, there have been numerous reported cases of adverse perceptual reactions.Hoyler CL, Tekell JL, Silva JA. Zolpidem-induced agitation and disorganization. Gen Hosp Psychiatry 1996; 18:452–453. One of these cases discusses an anorexic woman’s episode of macropsia, which occurred twenty minutes after taking 10 mg zolpidem. The same woman later had two more episodes of zolpidem-induced macropsia, after taking 5 mg and 2.5 mg zolpidem, respective to each episode. The intensity of the macropsia episodes decreased with the decreasing amount of zolpidem administered; it is implied in the article that the level of intensity was based on the patients accounts of her macropsia episodes, and that no external diagnosis was used.Iruela LM, Ibanez-Rojo V, Baca E. Zolpidem-induced macropsia in anorexic woman. Lancet 1993; 342(8868): 443-444. Hoyler points out notable similarities among the different reported cases of zolpidem-induced disorganization. The similarities were that all the cases were reported by women, the disorganization and agitation followed the first administration of zolpidem, and once zolpidem was discontinued, there were no lasting residual effects. It is believed that zolpidem-related macropsia is more prevalent in women because plasma zolpidem concentration is 40% higher in women, a concentration that further increases in anorexic women. Citalopram-induced macropsia is similar to zolpidem-induced macropsia since both types have been observed in relatively few cases, and neither of the drugs’ side effects can be supported by experimental evidence. Citalopram is an antidepressant that inhibits serotonin reuptake.Milne RJ, Goa KL. Citalopram. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in depressive illness. Drugs 1991; 41:450-477. The first case of macropsia thought to be induced by citalopram involves a woman who experienced macropsia after her first administration of 10 mg citalopram. Just as with zolpidem, after the immediate discontinuation of citalopram, there were no further episodes of macropsia.Ghanizadeh, A. Citalopram-induced macropsia. Clin Neuropharamcol 2007; 30(4): 246-247. Illicit drugs Temporary macropsia can be induced by a number of other illicit drugs. Various psychoactive drugs, such as LSD, psilocybin mushrooms (magic mushrooms), and marijuana can cause the user to hallucinate and experience macropsia. There are also suggestions that visual distortions, such as macropsia, can be associated with cocaine use.Unnithan SB, Cutting JC. The cocaine experience: Refuting the concept of a model psychosis? Psychopathol 1992; 25: 71-78. Episodes of temporary drug-induced macropsia subside as the chemicals leave the body. Migraine Past research has linked macropsia to migraine. One of these studies was conducted on Japanese adolescents who reported visual episodic illusions with macropsia and showed that illusions are three times more likely to occur in association with migraine. The illusions were most prevalent among girls between the ages of 16 and 18. It is unlikely that macropsia in Japanese adolescents could be due to epileptic seizure since only .3% of Japanese adolescents have epilepsy. No evidence of drugs was found, which eliminates the possibility of the macropsia in the adolescents being drug-induced. It is also unlikely for macropsia in adolescent children to be associated with a serious disease. It is usually the macropsia or other visual disturbance which precedes the painful migrainous headaches. The episodes of macropsia can occur as part of the aura in a migraine. These episodes are often brief, lasting only a few minutes. Adolescents who are deemed to have multiple distortions per episode, such as slow motion vision and macropsia, are even more likely to be sufferers of migraine. The macropsia episodes associated with migraine are typically equivalent to the duration of the aura, which can range from moments to 15 minutes. Non-migrainous headaches are not known to be associated with episodic illusions. Even in the absence of a migraine, a fever or a hypnagocic state can provoke visual illusions, which one might claim to be macropsia. A person with macropsia may fail to see the connection between the migraine and the macropsia, since the conditions may not elicit symptoms at the same time. The pathophysiology of the condition is not fully understood, but the timing of some episodic occurrences with the headaches suggests that there is a connection between macropsia and the vasoconstrictive phase of a migraine.Golden, Gerald S. The Alice in Wonderland Syndrome in Juvenile Migraine. Pediatrics 1979;63;517-519 The differences in visual phenomena, such as macropsia with slow motion versus macropsia without slow motion, may result from different areas of the brain being affected by migraine. Epilepsy Macropsia may present itself as a symptom of both frontal lobe epilepsy and temporal lobe epilepsy, which may actually help in the diagnosis of those diseases. Children who experience nocturnal hallucinations accompanied by macropsia may seek medical care for panic attack disorders and instead are diagnosed with forms of epilepsy. Epilepsy patients may have no memory of the seizure, but can remember the hallucinations and aura which proceed the attack. Electroencephalography, or EEG imaging, can then be utilized while the patient experiences the episode. It may be subsequently concluded that the EEG is congruent with temporal or frontal lobe seizure.Swash M. Visual perseveration in temporal lobe epilepsy J Neurol Neurosurg Psychiatry 1979;42:569–71. Anxiety and headaches accompany the episodes of visual distortion associated with epilepsy. Valproic acid is used to treat the epilepsy, and may be effective in ending the episodes of macropsiaZwijnenburg PJ, Wennink JM,Laman DM, Linssen WH. Alice in Wonderland syndrome: a clinical presentation of frontal lobe epilepsy. Neuropediatrics, 2002 33: 53-5. Hypoglycaemia Endogenous hypoglycaemia can result in number of visual disturbances and sometimes macropsia. This kind of hypoglycaemia is defined as having an abnormally low blood-sugar level due to anything other than the exogenous administration of insulin.Moorhouse D. Some Neurological manifestations of endogenous hypoglycemia. Brit Med J 1956; 2: 1512-1514. Macropsia has been observed in experimental hypoglycaemia and in patients receiving insulin therapy.Kalinowsky LB, Hoch PH. Shock treatments, psychosurgery and other somatic treatments in psychiatry. Grune and Stratton; 1952. Viruses Patients with both Epstein-Barr virus and infectious mononucleosis have cited an increase in the sizes of perceived objects, coinciding with other symptoms of Alice in Wonderland Syndrome.Cinbis M, Aysun S: Alice in Wonderland syndrome as an initial manifestation of Epstein-Barr virus infection (case report). Br J Ophthalmol 1992; 76:316 Additionally, it has been observed that Epstein-Barr patients who cite hallucinations display abnormal MRI scans. The MRI may show swelling of the cerebral cortex, transient T2 prolongation, and transient lesions. Unlike in MRI's, no abnormalities have been reported in CT scans. It is thus recommended that an Epstein-Barr patient who cites visual hallucinations have an MRI scanAtsushi Kamei, Makoto Sasaki, Manami Akasaka, Shoichi Chida. Abnormal magnetic resonance imaging in a child with Alice in Wonderland syndrome following Epstein-Barr virus infection No to hattatsu. Brain and development. 2002 Jul;34(4): 348-52,.Macropsia may appear either before the onset, or after the resolution, of all clinical symptoms associated with the illness.Lahat E, et al. Alice in Wonderland syndrome and infectious mononucleosis in children. J Neur Neurosur Psych 1990; 53:1104 The duration of the disturbances have been shown to range between two weeks and seven months. Almost all patients with macropsia due to infectious mononucleiosis have full recoveries. Patients with Coxsackievirus B1 have reported numerous symptoms of Alice in Wonderland Syndrome, the most common of which being macropsia and micropsia. Pathophysiology Macropsia may be a result of optical magnification differences between the eyes, retinal receptor distribution, or the cortical processing of the sampled image.Lancaster WB. Aniseikonia. Trans Am Ophthalmol Soc. 1938; 36:227-234. The current hypothesis for the occurrence of dysmetropsia is due to the stretching or compression of the retina leading to the displacement of receptors. Macropsia arises from a compressed receptor distribution leading to a larger perceived image size and conversely, micropsiaresults from stretching of the retina leading to a more sparse receptor distribution that gives a smaller perceived image size. In the case of macropsia, the greater density of photoreceptor cells leads to greater stimulation making the object seem larger.Ugarte M, Williamson TH. Horizontal and vertical micropsia following macula-off rhegmatogenous retinal-detachment surgical repair. Graefes Arch Clin Exp Ophthalmol. 2006; 244:1545-1548. In some cases, the effects of macropsia have been shown to be field dependent, in that the degree of visual distortion is related to the visual field angle. Non-uniform stretching or compression of the receptor distribution could explain the field dependency of the macrospia. If the compression forces were closer to the fovea the resulting compression would cause a greater amount of macropsia at lower field angles with little effect at higher field angles where the receptor distribution is not as compressed. Alterations in receptor distribution can be the result of epiretinal membrane, neuroretina detachment and/or re-attachment, or retinoschisis. Macropsia caused by surgical re-attachment of macula-off rhegmatogenous retinal detachment is not symmetrical around the fovea, resulting in differences size changes in the horizontal and vertical meridians. Asymmetry has also been observed with retinoschisis, in which macropsia generally results in the vertical direction while micropsia presents in the horizontal direction. Diagnosis Macropsia is generally diagnosed once a patient complains of the characteristic symptoms, such as disproportionally large objects in their visual field. The Amsler Grid test can be used to diagnose macropsia, along with other visual maladies depending on the subjective disturbance reported by the patient after looking at the Amsler Grid. Outward bulging of the lines on an Amsler Grid is consistent with patients experiencing macropsisa.Riley, H. D. (2005). Amsler grid testing. Indiana University School of Optometry. http://www.opt.indiana.edu/riley/HomePage/Amsler_Grid/4TEXTamsler_grid.html The New Aniseikonia Test (NAT) can quantify the degree of macropsia or micropsia independently in the vertical and horizontal meridians. The test consists of red and green semicircles on a black background with a white round fixation target. The size of the red semicircle is held constant while the green semicircle is varied in size in 1% increments. The patient wears a pair of red/green goggles so that one eye is tested at a time, and the patient attempts to determine when the semicircles are the same size. This is termed the reversal threshold and the size difference between the semicircles are reported as the degree of aniseikonia. A positive value indicates that the object was perceived bigger and thus corresponds to macropsia, and conversely a negative value indicates micropsia. The Aniseikonia Inspector contains an aniseikonia test based on the same principles as the NAT, but the test is run on a computer screen, it is based an a forced choice method, and it can measure the size difference as a function of the size of the objects. The functionality of being able to measure the size difference as function of the size (i.e. field depent testing) is especially important when the macropsia (or micropsia) has a retinal origin. Treatment The most common way to treat forms of aniseikonia, including macropsia, is through the use of auxiliary optics to correct for the magnification properties of the eyes. This method includes changing the shape of spectacle lenses, changing the vertex distances with contact lenses, creating a weak telescope system with contact lenses and spectacles, and changing the power of one of the spectacle lenses. Computer software, such as the Aniseikonia Inspector, has been developed to determine the prescription needed to correct for a certain degree of aniseikonia. The problem with correction through optical means is that the optics do not vary with field angle and thus cannot compensate for non-uniform macropsia. Patients have reported significantly improved visual comfort associated with a correction of 5-10% of the aniseikonia. With regard to drug-induced or virus-induced macropsia, once the underlying problem, either drug abuse or viral infection, is treated, the induced macropsia ceases. Research Future research may focus on ways to limit the occurrence of retinally-induced macropsia due to surgery. In terms of treatment, the most effective optical correction is still being researched with respect to visual field angles and direction to a target. The susceptibility of certain age demographics to macropsia is a subject that requires further validation.K. Abe, N. Oda, R. Araki, et al. Macropsia, micropsia, and episodic illusions in Japanese adolescents. Journal of the American Academy of Childhood and Adolescent Psychiatry 1989; 28:493–496. Overall, there have not been very many reports of macropsia induced by certain drugs, specifically zolpidem and citalopram. Once a larger effort is made to compile such reports, there will inevitably be more research on the subject of macropsia. References Category:Diseases of the eye and adnexa Category:Neurological disorders Category:Neuroscience Category:Optical illusions Category:Symptoms